Remove unused variable in compute and volume

This is to remove unused variable to keep code clean.

Change-Id: I055da09930e7ed8d5c6df589f50c68ae70b75010
diff --git a/tempest/api/compute/admin/test_servers_negative.py b/tempest/api/compute/admin/test_servers_negative.py
index 1283629..b53ced9 100644
--- a/tempest/api/compute/admin/test_servers_negative.py
+++ b/tempest/api/compute/admin/test_servers_negative.py
@@ -42,9 +42,7 @@
         super(ServersAdminNegativeTestJSON, cls).resource_setup()
         cls.tenant_id = cls.client.tenant_id
 
-        cls.s1_name = data_utils.rand_name(cls.__name__ + '-server')
-        server = cls.create_test_server(name=cls.s1_name,
-                                        wait_until='ACTIVE')
+        server = cls.create_test_server(wait_until='ACTIVE')
         cls.s1_id = server['id']
 
     def _get_unused_flavor_id(self):